1. Field of the Invention
The present invention relates to an improved electrolytic printing fluid and to a method of using the same. The method features the use of non-consumable electrodes.
2. Prior Art
In the electrolytic printing art there are at least two schemes for writing processes. In one such scheme, metallic ions from one of the electrodes are introduced into the printing sheet and they are either combined with colorless materials already present in the printing sheet in order to form colored complexes, or are precipitated as fine metallic particles. Exemplary of this scheme are those disclosed in U.S. Pat. Nos. 3,951,757 and 4,035,244.
In another scheme the electrodes are not consumed, the writing being accomplished by the electrolytic modification of materials already in the printing sheet. The scheme used the starch-iodine reaction to effect writing. Generally in this scheme, the electrolysis of potassium iodide or other iodide compound in the paper generates free iodine which reacts with the starch, also present in the paper, producing the widely known purple starch-iodide complex. The process of this scheme is fairly sensitive requiring moderately low current, e.g., 5.times.10.sup.-3 amps to about 5.10.sup.-2 amps, to produce a sufficiently dense image. Exemplary scheme of this type are those disclosed in U.S. Pat. Nos. 3,905,876 and 3,655,527.
Belonging to the latter class, it is also a dry electrolytic printing in which a very special paper is used consisting of one or two metallized layers.
Inherent in the last scheme are the disadvantages of requiring expensive paper requiring special layers of materials and the requirement of voltages that exceed 100 volts to print. See U.S. Pat. No. 3,511,700. Additionally, the consumable scheme suffers the additional disadvantages of having the stylus consumed in the process. This requires complicated printhead mechanisms with feeding devices to keep the stylus working. The non-consumable scheme suffers the further disadvantage of the lack of permanency due to fading of the printed works and the discoloration of the paper on storage.